Mark Yamauchi, the facilities operation manager at Toyota Motor Sales USA Inc., believes in solar power and is using it to partially power a large office complex. He has been using solar power long enough to learn a few things and offers some pointers to other facilities managers who may be considering it.

Toyota installed a 536-kilowatt system in 2003. The solar power provides 20% of the power needs of Toyota's south campus complex, a 624,000-square-foot building that's part of the company's national headquarters in Torrance, Calif. On some sunny weekends, the system, installed by PowerLight Corp. in Berkeley, Calif., may generate more power than needed by the building.

The system cost $3 million, but with state and federal tax credits, the actual cost to the company was about $1.5 million.

Here are four of Yamauchi's takeaways from using solar:

1. With tax credits, the original payback was estimated at about seven years. It's now at about nine years.

"We had an electric rate decrease, so everyone is happy about that except for me," Yamauchi said. "But it's still a good decision for the company," and rates are heading back up.

2. The solar panels are expected to last about 25 years. But Yamauchi knows the inverters, which convert direct current to alternating current, will have to be replaced before then, in 10 years to 15 years.

The need to replace inverters is "kind of the weak point in the system," Yamauchi said. The average replacement cost of an inverter is about 5% to 8% of the total cost of the solar system, according to one inverter maker that asked not to be named.

3. Maintenance costs are low. The panels are on the roof and occupy about 54,000 square feet. In the four years that the panels have been used, they have been washed four times, Yamauchi said.

4. Solar power doesn't raise specific IT issues. "It just augments the grid power for us," said Yamauchi.

But solar power is not an uninterruptible power supply, he said. As with most solar systems, it's attached to the electric grid, and if the grid goes down, so do the solar systems. There's a safety reason for that, he said, to protect linemen from electricity being generated by the system.

Despite Toyota's interest in solar power, it has not been adopted to any extent by IT managers as an alternative source.

Ken Brill, founder and executive director of The Uptime Institute Inc., a consultancy in Santa Fe, N.M., said the efficiency of solar systems is still low, and the cost is high and requires subsidies. "Things should make economic sense, and the private market will take care of it," he said.

Moreover, solar systems aren't resistant to hurricanes and other weather-related problems and their panels take up large amounts of space, Brill said. "It's not just the cost -- to me it's also the real estate" they need.